Turbine engines typically include a compressor section that draws air into the engine and compresses the air, a combustor section that mixes the compressed air with fuel and ignites the mixture, and a turbine section that converts thermal energy of the combustion process to rotational energy. It has been recognized that the state of the fuel when injected and combusted can affect performance of the turbine engine. For example, it is known that premixing the fuel with the compressed air prior to the mixture entering the combustor section can improve ignition and combustion of the mixture. As such, turbine engines are commonly equipped with fuel injector arrangements having a premixing chamber fluidly connected between the compressor section and the combustor section.
Although effective at improving combustion, premixing chambers can also be problematic. That is, it may be possible in some situations for the premixing chamber of the fuel injector arrangement to overheat and be damaged, to become fouled, to produce insufficient mixing, or to promote flashback (i.e., to promote flame propagation from the combustion chamber back into the premixing chamber). Thus, an improved fuel injector arrangement is desired.
An exemplary turbine engine having a premixing chamber is described in U.S. Pat. No. 3,937,007 (the '007 patent) issued to Kappler on Feb. 10, 1976. Specifically, the '007 patent describes a turbine engine having a premixing chamber bounded by porous ceramic walls, a combustion chamber immediately adjacent the premixing chamber, and a porous ceramic diaphragm separating the premixing chamber from the combustion chamber. Air is forced into the premixing chamber through the porous ceramic walls of the premixing chamber, as well as into the combustion chamber via openings in the combustion chamber. A fuel injector injects fuel into the premixing chamber, where it is atomized, extensively mixed with air, and vaporized without combustion. The vaporized air/fuel mixture then flows into the combustion chamber through pores of the ceramic diaphragm so that the mixture entering the combustion chamber is burned. The premixing chamber of the '007 patent assists combustion stabilization and attemperation, while reducing a required length of the combustion chamber.
Although the premixing chamber of the '007 patent may help improve combustion, it may still be sub-optimal. That is, the ceramic diaphragm that closes off the premixing chamber from the combustion chamber may create undesirable backpressures within the premixing chamber, be prone to clogging, and be susceptible to cracking under extreme pressures and temperatures. And, because the premixing chamber of the '007 patent is closed off from the combustion chamber by way of the diaphragm, the combustion chamber requires additional dedicated passageways to bring secondary and tertiary flows of air to the combustion chamber. These additional passageways can increase a complexity and cost of the turbine engine.
The disclosed fuel injector arrangement is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.